Process for the production of metals



IL-W

Oct. 7, 1958 w. c. F; HESSENBERG 2,354,732

' PROCESS FOR THE PRODUCTION OF METALS Filed March 11. 1952 Mun/0 (n/A Ike-05mm HESSENBEYRG Apt- .1m,

- Attorney United States Patent PROCESS FOR THE PRODUCTION OF METALS Wilfrid Cecil Frederick Hessenberg, Bromley, England, assignor to The British Iron and Steel Research Asso ciation, London, England, a British company Application March 11, 1952, Serial No. 275,964

1 Claim. (Cl. 29-528) This invention relates to the production of metals in elongated form, for example in the form of strip, wire or tube. 1

The invention provides what is in effect a novel method for the continuous casting of metals. Many methods of continuous casting have previously been suggested. To the best of our knowledge all these prior methods are characterized by the fact that the mould in which solidification of the melt takes place is external to the cast metal. With the present invention, however, the mould is internal and eventually forms part of the finished product, that is to say, the mould forms a core around which molten metal is cast.

Thus, there is provided in accordance with the invention the method of producing metal in elongated form which comprises feeding a core of metal in elongated form through a bath containing molten metal having the same composition as said core, the temperature of the bath and the rate of passage of the core through the bath being such that the core leaves the melt surrounded by a substantial deposit of metal from the bath which has solidified on the core, and thereafter reducing the thickness of the deposit-bearing core.

The invention also provides the method of producing metal in elongated form using a core of elongated form of the same metal, which comprises cleaning the surface of the core, passing the core, whilst it is at a relatively low temperature, through a bath of molten metal of the same composition as the core, the rate at which the core passes through the bath being such that there is substantial deposition of the melt upon the core due to solidification of the bath metal adjacent the core, and, after withdrawing the coated core from the bath passing it through thickness-reducing means.

The principle on which the invention works may be illustrated by the following example. If a piece of relatively cold metal is immersed in a bath of the same metal in the molten condition, heat will immediately flow from the adjacent part of the melt into the cold piece and a portion of the liquid metal will solidify and form a crust surrounding the piece. At this stage the piece must be withdrawn or, as more heat flowed into it from the liquid, the crust would remelt and eventually the piece itself would melt. This procedure, which is merely described to illustrate the principle of the invention, is not continuous, but may be made so as will be apparent from the following description of one method of performing the invention, which is given by way of eX- ample only, reference being made to the accompanying diagrammatic drawing. The drawing shows a side elevation, partly in section, of the basic apparatus for carrying out this method.

The invention will be described with reference to the production of steel, but it is also applicable to other metals. The core material comprises steel strip which has been freshly descaled and cleaned with an acid, such as sulphuric acid. The core material 10 is led from the coil 11, which is positively driven and passes between is to be reduced by hot working.

2,854,732 Patented Oct. 7, 1958 ICC 2 the bridle rolls 13, which the strip 10 passes into aholding furnace or bath 17 containing molten steel. A loop of the material 10 is formed between guide rolls 12 to take up any slack arising from the difference in speed at which the material leaves the coil 11 and that at which it passes through the bridle rolls 13.

The material 10 leaving the bridle rolls 13 is drawn through the furnace 17 by the bridle rolls 14. The bridle rolls 13 and 14 are linked (as indicated symbolically by the link 15), for example mechanically or electrically, so as to control the length of the loop of material which dips into the molten steel in the furnace 17.

The furnace 17 contains a weir 17a which prevents access of slag to the casting chamber 17b. Thecasting chamber 17b has a gas cover through which the material 10 enters the furnace, suitable gassealing means 17d being provided between the material 10 and the openings through which it enters and leaves the furnace 17.

During its passage through the molten metal in the bath, a crust will be formed on the material 10 as explained above. The temperature of the material and the bath, and the rate of passage of the material through the melt are adjusted so that it leaves the furnace surrounded by a substantial deposit of the solidified melt. The temperature of the bath must of course be maintained suificiently above the temperature at which the contents is molten, to prevent any danger of crust formation or the like, but there is no advantage in maintaining it at a higher temperature. The maximum time for the material to be immersed in the melt is that in which maximum deposition takes place without the danger arising of the deposited crust remelting. This time will clearly be dependent upon the metal concerned, the minimum cross-sectional dimension of the core material and the temperature difference between the melt and the core. By way of example, it may be stated that for steel strip /8 inch thick and of any width which can be handled in reducing mills, which is fed into a bath of molten steel at 1600 C., an immersion time of approximately 0.5 second gave a resultant strip of 4 inch thick. In this particular case the strip was moving through the furnace at the rate of 600 feet per minute so that the strip travelled approximately 5 feet through the bath. Under these conditions the interior of the strip reaches a temperature of about 1100 C.

It has been found that the time of immersion goes up approximately as the square of the minimum cross-sectional dimension of the core material. Thus for strip A inch thick the immersion time would be more than one second.

After leaving the bridle rolls 14 by which the material it) is drawn from the furnace 17, a further loop is formed between guide rolls 16. As the material passes between the rolls 16 it may be cooled if the material is to be put in temportary storage, or reheated if its thickness In the present example, the material is shown as passing via bridle rolls 22 to a rolling mill 23, where its thickness is reduced and is thence formed into a coil 24. Although only a single mill 23 is shown, the strip will in fact more likely be passed through a series of mills. Of course, other known methods of thickness reduction may be employed.

During the process of casting, working and cooling to room temperature the crystal structure of the metal is altered. New crystal grains grow within the metal and will be found freely disposed across the original junction of the core and the newly deposited metal. This effects a homogeneous bond and ensures that the junction is 'lJOlI a Source Of weakness.

control the speed at which If the coated strip is reduced to the original thickness of the core, part of it may be returned for a further passage through the bath, the remainder being equivalent to a new quantity of strip produced directly from the melt. It is a'specially advantageous feature of this invention thatthe rate at which solid metal is produced from the melt can be very high. The existing methods of con tinuous casting, with external moulds, are limited in rate of production by the time required to abstract sufficient heat from the relatively large volume of melt contained within the mould. Hitherto this has restriced their application to the non-ferrous metals industry where rates of production'are much lower than in the ferrous industry.

The invention is not restricted to the production of metal in strip form. Any of the continuously wrought metal forms, for example wire or tube, may be made by the same casting technique used in conjunction with appropriate methods of continuous thickness reduction.

As already stated, the amount of deposition is dependent on the temperature difference between the melt and the core, so that it would be possible to increase the maximum amount of deposition by pre-cooling the core. However, in general this will not be economical.

- I claim:

A method of producing steel in elongated form which comprises feeding a steel core in elongated form through a bath containing in molten form steel of the same composition as said core thereby building up on said core a substantial steel coating whereby the thickness of said core is increased, thereafter reducing the thickness of said core to its original thickness and returning a part of said reduced core to said bath for passage therethrough.

References Cited in the file of this patent UNITED STATES PATENTS 907,718 Beltzer et a1. Dec. 29, 1908 1,156,170 Page Oct. 12, 1915 1,289,260 Powanda Dec. 31, 1918 1,552,040 Fowle Sept. 1, 1925 1,896,411 Maskrey Feb. 7, 1933 2,034,278 Becket Mar. 17, 1936 2,175,706 Scott Oct. 10, 1939 2,384,086 Glock Sept. 4, 1945 2,424,418 Rory July 22, 1947 2,439,216 McLellan Apr. 6, 1948 2,457,420 Veeder Dec. 28, 1948 2,515,191 Carpenter July 18, 1950 2,544,671 Grange Mar. 13, 1951 2,567,685 Allen Sept. 11, 1951 

